Fume hood



Sept.. l1, 1934.

H. F. BUcKr-:L 1,972,917

, FUME HOOD Filed Feb. 2, 1932 Patented Sept. 1l, 1934 UNITED *STATESearner `otre-Ic:r:

FUME noon.`

Harold F. Buckel', Muskegon, Mich.

Applieatien February 2, 1932, Vserieu No. 590,478

9` claims. (o1. ess-115)k 'Ihis invention relates to improvements infume hoods for laboratory orother .uses` in which.-

fumes, along with a .quantity of room air, are initially drawn into. aplenum chamber located underneath the sloping roof of the hood and hencethrough a ilue to waste.

VIn known fume hoods the plenum chamber has been equipped with slidingdampers in its bottom by which the, operator, if he reached into thework chamber of the hood, could regulate .the rate ofV fume and air owfrom the .work chamber through the front and back apertures respective-Ely of the plenum chamben'but that inode of adjustment wasinconvenent.'and sometimes dan-.

gerous.

Air velocity through the doorway of the hood has usually been figured inprior devices at forty ve lineal feet per minute. This was, necessary toassure removing all of the fumes `and vapor. Nearly one half of this airhad to go intol the plenum chamber through the front aperture in orderto prevent the fumes from rising up. through the Work chamber to the.bfottom ofthe plenum chamber where they spread out umbrella shape inall directions. These rising gasesv sometimes traveled at two hundredfifty feet per minute.

To prevent this spread from getting out into.

the room, at least one half of' the air drawn into the apparatus had togo. into. the plenum chamber through the front opening, otherwise someof the fumes would puff out from under the lintel of the doorway. Withmy invention only one half the amount of air formerly required is nowneeded to prevent the gases puiling out as compared with the amount ofair required for a hood of the earlier type. Less warm air is removedfroin the room, consequently less heat is required to warm thelaboratory, and fuel for heating is saved.

My present invention relates to new and useful features of the bottomplate members. of the plenum chamber, including novel means foradjusting and controlling the rate of ilow into the front and rear inletpassageways of the said chamber; to a novel auxiliary battle and damperarrangement designed to. afford easy adjustment from the outside and toeffectually prevent any harmful tendency for the fumes at the top of thehood to accumulate behind the lintel of the front doorway and choke, andpuff outthrough the open front of the hood', under all conditions ofordinary use.. The invention is designed to simplify the construction ofprevious, fume hoods, to afford a max.-V

ofY strength and Stability while facilitating the manufacture andassemblage. of, the parts with consequent. economy in the commercialproduction of the article. 'Io` this end I have devised and invented theturner hood which isillustrated in the accompanying drawing hereafterdescribedin detail, my invention residing, ilrst, in the constructionand arrangement of the, ,ele` ments. constituting theV bottom Vof theplenum chamber, so as to utilize the bottom of the chamber asa meansforadjusting the gas now through the plenum chamber; 'seconda baillestructure constructed to prevent exposure of metallic parts` tocorrosion; third, in novel auxiliary adjust-A able means that shallprevent puiiing out at the.

front of the hood; fourth, in partition means that shall divide theascending column ofl fumes into two divergent streams, one flowingupwardly into the forward part ofthe plenum chamber and the otherflowing upwardly and rearwardly into the rear partof the plenum chamber,thus the partition prevents. fumes that have been drawn to. the upperrear section of the. hood from getting into the upper front section;vfifth, in a new andv improved structure of the vertical partition at therear of the work chamber, and means for actuating the damper at thebottom of the partition,

My improvement enables a smal-ler fan to be used at less initial cost,and less power is required Iin the motor that drives the fan; less. fanspace is required giving a more compact apparatus.v Smaller ducts canvbe used for handling the smaller amount of air and fumesy required vtobe exhausted, and consequently the cost. of ducts is reduced.

In the appended claims, I have pointed out the essential elements. ofmyinvention, it being unf. derstood, however, that. the claims arel notintended to be limited to the form ofA the parts illustratedandvdescribed further than a limitation to the described form isnecessary to distin. guish them from the prior art.

In the drawing Fig. 1 is a side view, partly broken away, of my novelfume chamber, the interior parts being indieatedby dotted lines and theilow of gas and of air bydotted arrows.

Fig. la is a fragmentary section showing diagrammatically the topportion of the hood and the arrangement ofthe baffles and'partitionstherein.'A v

Fig.' 2, is a front view of the hood shown in Fig. l'contracted inlength by being partly broken away.. 'q l Y' 'Fig 3 is a fragmentaryVhorizontalv I sectional view taken `on 1ine3-3 ofiFig. 1.

Fig. 4 is an enlarged sectional detail of the auxiliary front damper orbale.

Fig. 5 is an enlarged sectional view on line 5-5 of Fig. 2, showing apreferred construction of the damper at the bottom of the verticalpartition.

Fig. 6 is a face View of the parts shown in Fig. 5.

Fig. 7 is an end view, partly broken away, of a preferred structuralconnection between the two bafes that constitute the bottom of theplenum chamber.

Like reference numerals indicate like parts in all the figures in thedrawing.

The kind of fume hood to which my invention is adapted to be appliedconsists, as is shown in the drawing, of a cabinet structure providedwith a rearwardly and upwardly sloping vtop wall or roof 1 and aVentilating stack 2 leading'from the roof to waste, there being exhaustmeans, as a Ventilating fan (not shown) provided in the stack inl knownmanner.

The cabinet proper consists of a floor 3 on which the experimental orfume-generating apparatus 4 rests, a back wall 5, .two side walls 6, 6a,a front doorway 7 `and a lintel' above the front doorway,l its upperedge joining the lower part of the sloping roof 1.

l Just beneath the roof is a space 9 termed the plenum chamber which isdened by the roof and by deilecting plates 10, 10a spaced below theroof, extending from side wall6 to wall 6a, and preferably divergentupwardly, the arrangement being such that the column of fumes 11ascending f in the work chamber is compelled to divide, by

Y plenum chamber, part of the fumes entering thev means of a verticaldivider 12 that spans the hood from side to side beneath the bottom ofthe plenum chamber 9 at a Vfront inlet aperture 9a, the remainder at arear aperture 9b. The plenum chamber contains a body of fumes and air ofsufficient volume to smooth out any irregularities or pulsationsproduced Vby the exhaust fan and causes'a practically constant suctionvin the work chamber. The intensity of such suction is regulated byvarying the openings 9a, 9b that are dened by the spacing of the edgesof plates 10, 10a from adjacent walls of the hood, as roof 1, and theinner wall or partition 13, which will be described later. My inventionincludes means for accomplishing such adjustment without requiringV theoperator to reach into the fume hood, that is, the adjustment may beeffected solely from outside the hood while fumes are being generated init. The adjustment may be produced by various mechanical means, butmerely for purpose of illustration, and not as a restriction to thescope of the invention, I havey shown a preferred adjusting means.

In the form shown, the front deecting plate 10 and the rear plate 10o,constituting the bottom of the plenum chamber are rigidly unitedohliquely to each other and divergent upwardly. The bottom thus formedcan be raised and lowered to adjust the size of the front and rear inletapertures 9a, 9b. To permit the plenum chamber bottom to be adjusted bymeans that can be worked fromoutside the hood, I prefer to provide threeslots in each side wall 6, 6a of the cabinet. Through each slot projectsa threaded guide pin, there being one pin 10', 10a', on each end of eachplate and one on each end of the junction of the two plates, as shown at9c in Figs. 1 and 7. Fasteners, such as wing nuts and washers, are usedfor clamping the plates ,10, 10a to the walls of the cabinet. When thewing nuts are loosened the desired adjustment of apertures 9a, 9b ismade by moving both plates 10, 10a. This may be conveniently done bymeans of an adjusting lever 9d pivoted at 9e to the side wall of thecabinet, the pin 9c projecting into the end of the lever.

An upright partition 13 is, as usual, spaced from the back wall 5 andextends up to the plenum' chamber, the vertical ue so defined being incommunication at its bottom with the work chamber and at its top withtheexhaust stack so as to remove fumes from the lower part of the workchamber. The upper part of the upright partition is bent forward at 13ato conform to the plate 10a of the plenum chamber in its adjustment. Atits bottom the partition 13 hasl an` opening v13h controlled by anadjustable damper 14 hinged at its lower edge. The damper passes anamount of air suiiicient to carry off gases that are heavier than air.

The preferred means for adjusting damper 14 is illustrated in Figs. 5and 6, there being an eye 15 loosely connected to the upper or openingedge of the damper, the shank of the eye passing through a hole in thepartition 13 and connected to an adjusting push-rod 15a extendingforwardly to a convenient place within the reach of the operator. ,Alatch 15 is pivoted to the partition and shaped to present an eccentricslot 16a to engage the adjusting rod Yby camaction so as to hold thedamper in any adjusted position.

A claimed feature of my invention is an auX- iliary adjustable member,such as baiiie'plate or damper 17, located rearwardly of the lintel 8 ofdoorway 7, slightly. above its lower margin and below the deecting plate10 of the plenum chamber. The purposeof auxiliary damper 17 is to sodirect the main part of astream of room air entering the doorway underthe action of the eX- hauster in the stack, that. it shall ilowrearwardly toward and into the front uprising stream of fumes, thusexerting a tendency Vto keep the fume stream against divider 12, therebyprevent.

ing puing out through the doorway. Moreover, auxiliary damper 17 permitsa relatively small and controllable part of the incoming stream of room'air to pass through opening 17a adjacent the lintel 8, up the back wallof the lintel and thence along the under side of the roof 1 of the hoodinto the plenum chamber. This thin stream of room air there mingies withthe front ascending stream of fumes and assists in directing those fumesinto the plenum chamber. The incoming room air is thus divided by damper17 into twov air curtains that operate to keep the fumes iii-- side thehood and lead them to the stack. To

tiltingly adjust damper 17, which is mounted on xed pivots 17D carriedby the sidewalls 6, oaV

of the hood, wing nuts 18 are provided on threaded pins 19 that projectfrom the ends of the` damper through arcuate slots 20 in the side f:

wall.- Simultaneous adjustment can then be made of the amount of airtaken through opening 17a back of lintel 8 and thence up under the hood,also of the amount of room air taken horizontally into the work chamberto counteract any j:

or intermediate chamber 21 in advance of the .-f-

plenum chamber. Through vthis vintroductory chamber must pass the risingfront portion of the main column of fumes and also the air stream thatisrtaken in through the upper part of the.

doorway, before they can enter the front inlet LIQ aperture 9a of theplenum chamber. The lintel 8, roof 1, and front deecting plate 10 of theplenum chamber bottom constitute the other walls that, together withdamper 17, define the introductory chamber 21. The purpose of thischamber is to further minimize pulsation of the gases and prevent pufngout.

The dampers and partitions as shown in Figs. 1, 2, 3, 4 and '7 may bemade of asbestos slabs or plates that are preferably mounted in cleftsformed in the flanges Yof obtuse angle member 22, 22a. The plates aresecured to members 22, 22a by bolts, and to prevent corrosion thosemembers and their bolts are covered with a protective layer 23 ofasbestos or the like.

With the baiile and damper arrangement of my invention the fume hoodwill automatically separate the ascending column of fumes into twoparts, drawing one part rearwardly into the plenum chamber and drawingthe relatively small residual part into the forward end of the samechamber. The residual part of the fumes is entrained with a small, butsteady flow of room air into the introductory chamber and this incomingroom air is, by means of auxiliary baffle 1'7, converted into a iiowingair curtain that prevents fumes from puflng out.

Having thus described my invention, what I claim and desire to protectby Letters Patent is:

l. In combination, a walled fume hood including a plenum chamber havinga bottom comprising plates oblique and divergent upwardly, their edgesspaced from the walls of the hood, adjusting means adapted to move saidplates simultaneously toward or away from the walls of said hood, saidadjusting means operable from outside the hood, an upright partitionspaced from the rear wall of the hood, the upper end of said partitioninclined toward and spaced from the rear upper edge of the bottom ofsaid plenum chamber, the said partition having an opening at its lowerend, a hinged damper at said opening and actuating means thereforoperable from outside the hood, latch means releasably securing saiddamper, a vertical divider plate below the plenum chamber, an auxiliarydamper forward of the plenum chamber and in front of the divider plate,having its forward edge spaced from the front wall of the hood topresent an air passage, and adjusting means for said auxiliary damper.

2. In a fume hood including a plenum chamber, the bottom of said chambercomprising two deflecting plates oblique to each other, divergentupwardly and extending across the hood from side to side and a verticaldivider spanning the hood from side to side beneath said plenum chamberbottom, and an auxiliary baiile means positioned lower than the plenumchamber and in front of the divider plate, the bottom of the plenumchamber and the auxiliary barile means dening an introductory chamber.

3. In a fume hood including an upwardly and rearwardly inclined roof, aplenum chamber, having a bottom comprising two deiiecting plates obliqueto each other, divergent upwardly, and extending from side to sideacross the hood, a doorway having a downwardly projecting lintel,

an auxiliary damper member located beneath the roof back of the linteland in front of and beneath the plenum chamber, said damper member,together with the bottom of the plenum chamber, defining an introductorychamber, the lintel and the forward edge of said damper member spacedapart and presenting an opening for intake of air.

4. In a fume hood including a doorway, a lintel and a plenum chamber,having a bottom comprising two deflecting plates oblique to each other,divergent upwardly, and extending from side to side across the hood, adamper located in front of the plenum chamber and spaced from thelintel,

said damper being substantially horizontal, and damper-actuating meanslocated outside the hood and adapted for adjustment to vary the spacedrelationship of said damper and lintel.

5. In a fume hood including a plenum chamber having inclined top andrear walls, a bottom for said chamber comprising plates ilxedly joinedtogether oblique to each other and upwardly divergent and having theircommon edge movably mounted on the hood, and means operative fromoutside the hood adapted to actuate said plates simultaneously so as tomove their outer edges into various adjusted positions in relation tosaid top and rear walls and to thereby alter simultaneously the frontand rear fume passageways into said plenum chamber.

6. In a fume hood including a plenum chamber, a movable bottom memberfor said chamber, said bottom member spanning the hood from side toside, and comprising two divergent baffles xed together at their commonlower edge, adjusting devices operatively connected to said baitlemembersV and adapted to variously position the same by simultaneousmovement relatively to the top and rear Walls of the hood.

'7. In a fume hood having a plenum chamber and inlet apertures therefor,a bottom for said chamber comprising upwardly divergent deilectingplates, a mounting for said plates comprising an angle member havingcleft flanges receiving adjoining edges of said plates, and actuatingmeans operatively connected to said angle member and adapted to move thesame to various adjusted positions whereby to effect correspondingadjustments of said plates for varying the size of said inlet apertures.

8. A fume hood including a plenum chamber, a bottom member for saidplenum chamber consisting of two deecting plates positioned oblique toeach other and extending divergent upwardly, the upper end of saidplates being adjustably spaced from the top wall ofthe hood to providean inlet aperture to said plenum chamber, the upper end of the otherplate being adjustably spaced from a rear wall of the hood, and meansfor effecting such adjustments simultaneously.

9. In a fume hood having side walls formed with slots, an auxiliarybale, a plenum chamber having a movable bottom, guide pins lixed to saidbarile and guide pins on the bottom of the plenum chamber, said pinsprojecting through said slots, and fastening means adapted to securesaid pins at various locations in said slots.

HAROLD F'. BUCKEL.

